"I think they're the best team in the NBA, but I wouldn't call them a great team. I wouldn't rank them anywhere near the top 10 best teams ever," Frazier said Friday on ESPN New York 98.7 FM's "The Michael Kay Show."
The Heat (53-14) have won 24 games in a row and are trying to break the NBA record of 33 set by the 1971-72 Los Angeles Lakers.
"It's more an indication of how weak the NBA is right now than their superiority," Frazier said.
Frazier doesn't think the Heat will break L.A.'s record.
"I never thought that that record would ever be matched, and Miami is close, but I don't think they're going to do it. You know why? They're struggling," Frazier said.
"When we [the Knicks] were the first team in 1969-70 to win 18 consecutive games, the starting five was on the bench in the fourth quarter. I mean, we were blowing teams out. Miami is not blowing teams out; they're making miraculous comebacks.
"So I think sooner or later it's gonna catch up with them. The other problem is they're playing mediocre teams. They're playing teams that have nothing to lose and they're looking to make their season by breaking that streak, so I think that's going to eventually cause their demise."
Six of Miami's next 10 games are against teams with losing records.
Asked who would win in a game between the 1995-96 Chicago Bulls, who won a league-record 72 games, or this Heat team, Frazier said, "C'mon. The Bulls. Please don't say that this is a great team, guys. These guys maybe have two [future] Hall of Famers. C'mon. This is not a great team."